Think: Happy, at rest, may all beings be happy at heart. Whatever beings there may be, weak or strong, without exception, long, large, middling, short, subtle, blatant, seen & unseen, near & far, born & seeking birth: May all beings be happy at heart. Let no one deceive another or despise anyone anywhere, or through anger or irritation wish for another to suffer. As a mother would risk her life to protect her child, her only child, even so should one cultivate a limitless heart with regard to all beings. With good will for the entire cosmos, cultivate a limitless heart: Above, below, & all around, unobstructed, without enmity or hate. Whether standing, walking, sitting, or lying down, as long as one is alert, one should be resolved on this mindfulness. This is called a sublime abiding here & now. Not taken with views, but virtuous & consummate in vision, having subdued desire for sensual pleasures, one never again will lie in the womb.
Think. But be prepared for the unknown and hypothetical "nutjob" who might attack and threaten that which is most dear to you.
Be prepared for ALL eventualities. Establish yourself with the means to put him away.For good if necessary. You have the right to bear arms. With a limitless heart.